Currently there are many occasions where secure vehicle access to a location such as a parking lot or parking garage is desirable. The parking lot or garage may be associated with an office building, an apartment building, a condominium development or the like. It is known in the art to provide vehicle access via a radio frequency transmitter that transmits a signal modulated with an identity code. A receiver located within the parking lot or garage demodulates received radio frequency signals. If the receiver determines that the received identity code is an authorized identity code, a door or other access barrier is opened. This permits the vehicle to enter the controlled space. In the known art, the authorized transmitters have the same identity code or one of a limited number of identity codes. Likewise, the receiver responds to only this limited number of identity codes.
There is a problem with prior art systems. These prior art systems do not distinguish between the various transmitters. Systems of this type used with large buildings have a certain amount of turn over of clients on a regular basis. Thus there are generally several formerly authorized users who are now unauthorized. In the prior art systems such formerly authorized uses could not be easily locked out without return of the transmitter. It is impractical to reprogram the receiver and the transmitters of the still authorized users each time a former client retains possession of a transmitter. These formerly authorized users thus compromise the security of the system.
A further problem is called pass back. An authorized user may use his transmitter to enter the parking lot or garage and then retrigger the door with the transmitter. This again opens the door allowing an unauthorized entry. Prior art systems cannot prevent this unauthorized use.
There is therefore a need in the art for a more secure system for control of vehicle access to a parking lot, garage or like structure.